Use this list to identify Marin's most common fire-prone plants. These plants ignite readily and burn intensely, and should be avoided (or removed, if noted) if present in a home's Defensible Space zone or close to roads and driveways. If removal is not an option, intensive maintenance may be required to reduce flammability. Your fire department may require removal of the plants on this list within 100' of structures.
This list is not comprehensive and is intended to identify only the species most common in Marin. Learn more about fire-prone plants.
Firs (Abies) are a genus of 48-56 species of evergreen coniferous trees. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range. Firs are most closely related to the genus Cedrus (cedar). Douglas firs are not true firs, being of the genus Pseudotsuga.
They are large trees, reaching heights of 10-80 m (33-262 ft) tall and trunk diameters of 0.5-4 m (1 ft 8 in-13 ft 1 in) when mature. Firs can be distinguished from other members of the pine family by the unique attachment of their needle-like leaves and by their different cones.
Identification of the different species is based on the size and arrangement of the leaves, the size and shape of the cones, and whether the bract scales of the cones are long and exserted, or short and hidden inside the cone.
A popular, drought tolerant grass that forms clumps of purplish maroon blades topped with rose-red flower spikes. While attractive as a landscape specimen or planted in groups, this grass is fire prone and should be removed in the defensible space zone.
French broom (Genista monspessulana) is a fire prone, upright, evergreen shrub, commonly to ten feet tall. The round stems are covered with silvery, silky hair, and the small leaves are ususally arranged in groups of three. About eighty-five percent of the photosynthetic tissue of French broom is in leaf tissue. The small (less than half-inch) yellow flowers are pea-like and clustered in groups of four to ten. The mostly inch-long pods are covered with hairs.
This species sometimes is confused with Scotch broom (Cytisus scoparius), which has pods with hairs only at the seam, green stems that are five-angled and ridged, flowers that are golden yellow and larger than half an inch, and only about fifty-five percent of total green tissue as leaves.
French broom is found primarily in central coastal counties from Monterey County north to Mendocino County and inland in Lake, Solano, and Contra Costa counties. It is also known from Del Norte County, northern Sierra Nevada foothill counties to 800 meters, and in Kern, San Bernardino, and San Diego counties.
This broom is common on coastal plains, mountain slopes, and in disturbed places such as river banks, road cuts, and forest clearcuts, but it can colonize grassland and open canopy forest. It is found growing in varied soil moisture conditions, but prefers siliceous soils. Unlike other broom species in California, it grows reasonably well on alkaline soils with pH 8. It is competitive in low-fertility soils because of mutualistic relationships with nitrogen-fixing bacteria found in small nodules on roots.
French broom currently occupies approximately 100,000 acres in California. It displaces native plant and forage species, and makes reforestation difficult. It is a strong competitor and can dominate a plant community, forming dense monospecific stands.
Common gorse (Ulex europaea) is a prickly evergreen shrub less than ten feet tall, with a profusion of yellow pea-like flowers from March to May. By May plants are covered with half-inch- to one-inch-long brown pods. The short, stout branches are densely packed and may appear leafless. Spines, approximately half an inch long, are located at base of leaves. The somewhat similar species, Scotch broom (Cytisus scoparius), is not prickly.
orse may be slow in spreading and becoming established, but where it gains a hold, there are few other plants that will so completely dominate an area. Besides becoming a significant fire hazard, it can successfully outcompete native plants in part because of its association with nitrogen-fixing bacteria, which facilitate its colonization of nitrogen-poor soils. Gorse leaf litter acidifies and lowers the cation exchange capacity of moderately fertile soils by immobilizing the bases, making it more difficult for native species to establish. On San Bruno Mountain, San Mateo County, gorse is considered the most difficult exotic species to control, and it has caused considerable loss of valuable grassland habitat.
Tsuga is a genus of conifers in the pine family Pinaceae. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliage to that of the unrelated plant poison hemlock. Unlike the latter, Tsuga species are not poisonous.
Eight to ten species are within the genus (depending on the authority), with four species occurring in North America and four to six in eastern Asia.
They are medium-sized to large evergreen trees, ranging from 10-60 m (33-197 ft) tall, with a conical to irregular crown, the latter occurring especially in some of the Asian species. The leading shoots generally droop. The bark is scaly and commonly deeply furrowed, with the colour ranging from grey to brown. The branches stem horizontally from the trunk and are usually arranged in flattened sprays that bend downward towards their tips.
Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Junipers (Juniperus spp.) are one of the hardiest, most versatile and drought-tolerant shrubs. They are also one of the most fire prone species, and are sometimes referred to as a "gasoline bush" by firefighters. They are conifers with prickly young foliage that becomes flatter and softer with age.
Junipers should be removed within 30' or structures and 15' of roadways and driveways. Period.
Any junipers remaining in the defensible space zone (from 30' to 100') must be maintained completely free of dead needles and twiggy material, should be irrigated every 2 weeks, and should be thinned and separated into individual bushes.
Should also be kept widely spaced from one another and regularly maintained by thinning and pruning out ALL dead branches and twigs. When well maintained, most manzanita species are relatively fire resistant. Without proper maintenance, manzanita can contribute significantly to wildfires - based on this, it should be avoided in the defensible space zone of houses in Marin's WUI.
Cortaderia selloana and Cortaderia jubata, Pampas grass or Jubata Grass, are species of grass known by several common names, including purple pampas grass and Andean pampas grass. Jubata is similar to its more widespread relative, the pampas grass Cortaderia selloana, but it can get quite a bit taller, approaching seven meters in height at maximum.
All Corataderia are fire prone and should be avoided or removed in the defensible space zone.
Pine trees (Pinus spp.) are the most common coniferous tree worldwide, numbering around 100 species. These trees form large forests characterized by wide open areas with sunlight spilling to the forest floor. Pines are sun-loving trees that do not grow well under shady conditions.
All pines are prone to fire, and may contribute significantly to wildfires.
Rosmarinus officinalis, commonly known as rosemary, is a woody, perennial herb with fragrant, evergreen, needle-like leaves and white, pink, purple, or blue flowers, native to the Mediterranean region.
Scotch broom (Cytisus scoparius) is an invasive perennial shrub six to ten feet tall. Its sharply angled branches generally have five green ridges with hairs on them when young; as the branches mature the hairs fall off, and the branches become tan and lose the distinct ridges. Pods have hairs along the seams only. One or two golden yellow pea-like flowers cluster between the leaf base and stem. About half the photosynthetic (green) tissue is in the leaves and half is in twig tissue. Sometimes this species is confused with French broom (Genista monspessulana), which has pods with hairs all over them, stems that are not ridged or green, and more than eighty-five percent of its photosynthetic tissue in leaf tissue.
Found along the California coast from Monterey north to Oregon border, Scotch broom is prevalent in interior mountains of northern California on lower slopes and very prevalent in Eldorado, Nevada, and Placer counties in the Sierra Nevada foothills. It is also reported from Los Angeles and San Bernardino counties. It is common in disturbed places, such as river banks, road cuts, and forest clearcuts, but can colonize undisturbed grassland, shrubland, and open canopy forest below 4,000 feet.
Scotch broom currently occupies more than 700,000 acres in California. It displaces native plant and forage species and makes reforestation difficult. It is a strong competitor and can dominate a plant community, forming a dense monospecific stand. Seeds are toxic to ungulates. Mature shoots are unpalatable and are not used for forage except by rabbits in the seedling stage. Foliage causes digestive disorders in horses (Parsons 1992). Since Scotch broom can grow more rapidly than most trees used in forestry, it shades out tree seedlings in areas that are revegetated after tree harvest. Scotch broom burns readily and carries fire to the tree canopy, increasing both the frequency and intensity of fires (Parsons 1992). This species is difficult to control because of its substantial and long-lived seedbank.